1. Field of the Invention
The present invention relates to an analytical method for use in electron microscopy and, more particularly, to an analytical method of making an X-ray analysis of a specimen using a scanning transmission electron microscope or scanning electron microscope.
2. Description of Related Art
A scanning transmission electron microscope having analytical capabilities is designed to make X-ray analyses of certain points on a specimen, as well as to image the specimen in a normal manner. In this analytical mode, the specimen position and the magnification are so controlled that a point within a secondary electron image to be analyzed comes within the observed region. Then, a sharply focused beam is directed at the point to be analyzed.
As the specimen is irradiated with the electron beam in this way, characteristic X-rays are produced. The X-rays are detected by an energy-dispersive X-ray detector, for example. Where there are plural analysis points, the specimen stage and the magnification are controlled in such a way that X-ray analyses of the analysis points are carried out while controlling the specimen stage and magnification to bring each analysis point to within the observed region.
Where settings are made on previously obtained images and plural analysis points are analyzed in succession in the analytical mode, the specimen stage is controlled during the analysis sequence. However, the positional accuracy of the stage is not always sufficiently high and so it is difficult to reproduce the analysis points accurately. As a result, the electron beam may be directed at positions deviating from the set analysis points.
In view of the foregoing, the present invention has been made. It is an object of the present invention to provide an analytical method which is for use in electron microscopy and capable of precisely directing an electron beam at set analysis points and performing analyses.
This object is achieved by an analytical method comprising the steps of: obtaining a first image of a specimen as a reference image when the specimen is in a first position; storing the reference image and the first position of the specimen in memory; specifying an analysis point within the reference image; storing the coordinates of the specified analysis point in memory; returning the specimen into a second position according to the stored position of the specimen; obtaining a second image in the second position; comparing the second image with the reference image and calculating the amount of deviation in position between both images; and correcting the amount of deflection of the electron beam based on the calculated amount of deviation between the images and shining the beam at the analysis point to thereby perform an analysis of the analysis point.
The present invention also provides an analytical method comprising the steps of: obtaining plural first images of a specimen; synthesizing the first images into a synthesized image; setting an analysis point in the synthesized image; extracting an area of a given magnification including the analysis point to create a reference image; obtaining a second image of the area including the analysis point at the given magnification; comparing the second image with the reference image and calculating the amount of deviation in position between both images; and correcting the amount of deflection of the electron beam based on the calculated amount of deviation between the images and shining the beam at the analysis point to thereby perform an analysis of the analysis point on the specimen.
Other objects and features of the present invention will appear in the course of the description thereof, which follows.